Study Guide Eruvin 36 Today’s daf is dedicated by Rachael Bentley. “I am so very grateful to be able to participate in this cycle of Daf Yomi and want to thank you all. Who would have thought at the outset that we would be living in such strange times? My Montreal group arranged to meet as we finished Tractate Berakhot but of course...even as we finished Tractate Shabbat, we have still not met in person but also by the miracle of Zoom. My prayer is to meet in Israel after completing, by the grace of God. Many thanks and my wishes for good health and safety for all.” And in honor of Jonathan Cohen, my brother, on his birthday today, who has been keeping up with the daf. The gemara raises a contradiction from Rabbi Meir in our mishna who is stringent regarding an eruv that was good to begin with but later is not (one must assume it was not valid already during twilight) with Rabbi Meir in a different source regarding impurity where he is lenient. Two explanations are brought. Likewise, a contradiction is brought regarding Rabbi Yossi who is lenient in our mishna but stringent elsewhere. Three possible explanations are brought. When does one rely on its original chazaka and when do we not? If one makes a stipulation regarding an eruv - whether or not that will be one's eruv, does that work? On what does it depend? Rabbi Yehuda allows one to decide on Shabbat which one will be the eruv. How can this be if: 1. Ayo has a version of the braita that says he doesn't allow this, and 2. We know from other sources that Rabbi Yehuda doesn't allow breira, retroactive determination?